The present invention relates to a packet transmission apparatus for transmitting compressed coded image data, audio data and additional information data or general data in a packet form by way of a transmission line.
In recent years, the capacity of communications has remarkably increased according to development of communications systems utilizing optical fiber cables and the like, and digital transmission systems for transmitting not only digital data for use in computers and the like, but also, for example, an image signal, an audio signal and the other additional information after being digitized has been put into practical use.
For example, use of an asynchronous transfer mode (referred to as an ATM hereinafter) or the like enables transmission at a rate of not lower than 155 megabits per second, and an ATM transmission system for transmitting image data by way of an ATM transmission line has been put into practical use.
In regard to the ATM transmission system, there is provided standardization through discussions by ITU-T (International Telecommunication Union-Telecommunication Standardization Sector), The ATM Forum and so forth, and many relevant documents have been published.
For example, a prior art for communicating a video signal in a packet form is disclosed in the prior art reference of U.S. Pat. No. 5,159,452 (referred to as a prior art hereinafter).
In the prior art, an example in which a packet loss position (packet loss information) is known and loss correction is executed is shown in FIGS. 6A and 6B of the prior art, and an example in which error correction is executed is shown in FIG. 7 of the prior art.
However, the prior art construction as described above has had the following problems.
(1) When handling communications in, for example, the ATM, transmission is executed in a unit of packet of 53 bytes called a cell. If a packet loss (cell loss) occurs, then the cell is lost within the ATM network, and therefore, this leads to such a problem that the occurrence of the cell loss within the ATM network cannot be detected from the information of the cell itself received by a reception terminal. As is natural for the above reasons, there has been such a problem that the position in which the cell loss has occurred cannot be identified. Therefore, the loss correction that must essentially identify the position of the error (cell loss) is impossible unless a special constituent factor for informing the reception terminal of the occurrence of the cell loss from the network side is provided. provided.
(2) Although the identification of the error position and correction are enabled by using the error correction method shown in FIG. 7 of the prior art, the method has had such a problem that the efficiency is low when the error correction is executed in terms of the number of errors that can be corrected with respect to the parity amount for error correction use to be added, i.e., the total amount of transmission and the number of error corrections (error correcting performance).
There has been such a further problem that the probability of the occurrence of cell loss disadvantageously increases due to the congestion of the ATM network when the total amount of transmission increases.
(3) In the ATM, an ATM adaptation layer (referred to as an AAL hereinafter) is prescribed by the standard of ITU-T Recommendation, and there are many types of equipment that cope with the standard. However, the prior art, which does not use the universal AAL function, has had such a problem that, for example, the error detection of the AAL type 5 cannot be utilized. It is also essential to independently input, for example, the function that a signal representing the breakpoint of a sequence of a video signal must be independently inputted, for which the transmission efficiency is low and no universal equipment can be used, and this leads to such a problem that no interconnecting capability exists.
There has also been such a problem that the processing circuit scale is large, and a cost is very high since no universal equipment can be used.
A first object of the present invention is to provide a packet transmission apparatus capable of enabling transmission tolerating packet loss (cell loss) by reducing the probability of the occurrence of the packet loss (cell loss) and improving the reliability of real-time communications.
A second object of the present invention is to provide a packet transmission apparatus capable of effectively utilizing a communications zone, enabling the ATM layers to be utilized from upper layers and easily using the currently popularized or prevailed ATM equipments.
A third object of the present invention is to provide a packet transmission apparatus capable of improving the error correction efficiency and error correction capability with respect to the amount of parity added by executing error correction or error detection, enabling the ATM layers to be utilized from upper layers and easily using the currently popularized ATM equipments.
Furthermore, a fourth object of the present invention is to provide a packet transmission apparatus that has a simpler apparatus construction and is less expensive as compared with the prior art.
According to the first aspect of the present invention, there is provided a packet transmission apparatus for transmitting in a packet form a transmission unit including a data string arranged so as to divide predetermined data into a plurality of blocks, each block having a fixed length, wherein block information for specifying a block type is added to each block. The packet transmission apparatus according to the first aspect of the present invention comprises generating means for generating a transmission header having a new identifier by deleting predetermined redundancy information from the block information belonging to the plurality of blocks based on said data string, and generating a transmission unit having the generated transmission header, and transmitting means for transmitting the transmission unit generated by said generating means by way of a transmission line.
generating means for generating a transmission header having a new identifier by deleting predetermined redundancy information from the block information belonging to the plurality of blocks based on said data string, and generating a transmission unit having the generated transmission header; and
transmitting means for transmitting the transmission unit generated by said generating means by way of a transmission line.
Also, in the above-mentioned packet transmission apparatus, the generating means preferably generates a new identifier by making the information of one block represent the information of the plurality of blocks, and generates a transmission header having the generated identifier.
Further, in the above-mentioned packet transmission apparatus, the generating means preferably makes the information of one block represent the information of an identical block.
Furthermore, in the above-mentioned packet transmission apparatus, the generating means preferably deletes the redundancy information including at least one of reserved data and invalid data.
Also, in the above-mentioned packet transmission apparatus, the transmission header preferably includes a time code and a serial number.
Further, in the above-mentioned packet transmission apparatus, the transmitting means preferably transmits the transmission unit by an ATM transmission system using the AAL TYPE 1 as an adaptation layer function of an asynchronous transfer mode.
Furthermore, in the above-mentioned packet transmission apparatus, the transmitting means preferably transmits the transmission unit by an ATM transmission system using the AAL TYPE 5 as an adaptation layer function of an asynchronous transfer mode.
Also, in the above-mentioned packet transmission apparatus, the transmitting means preferably adds a parity for error correction to the generated transmission unit, thereafter, executes an interleave process on data including the added parity for error correction, and outputs data obtained after the interleave process as a transmission unit.
Further, in the above-mentioned packet transmission apparatus, the generating means preferably executes the interleave process by writing the data including the added parity for error correction into a storage apparatus having a matrix form in a first direction of the matrix, and thereafter, reading from the storage apparatus the data in a second direction perpendicular to the first direction of the matrix.
According to the second aspect of the present invention, there is provided a packet transmission apparatus for transmitting in a packet form a transmission unit including a data string arranged so as to divide predetermined data into a plurality of blocks, wherein each block has a fixed length. The packet transmission apparatus according to the second aspect of the present invention comprises a first interleave processing means for executing a first interleave process by writing the data string into a first storage apparatus having a first matrix form in a first direction of the first matrix, and thereafter, reading from the first storage apparatus the data in a second direction perpendicular to the first direction of the first matrix, and for outputting the data obtained after the first interleave process in a unit of data in the second direction, parity adding means for adding a predetermined parity for error correction to data outputted from the first interleave processing means in a unit of data in the second direction, and outputting the data to which the parity for error correction is added, second interleave processing means for executing a second interleave process by writing data outputted from the parity adding means into a second storage apparatus having a second matrix form in a fourth direction of the second matrix coinciding with the second direction of the first matrix, and thereafter, reading from the second storage apparatus the data in a third direction perpendicular to the fourth direction of the second matrix, and for outputting the data obtained after the second interleave process in a unit of data in the third direction, and transmitting means for transmitting data outputted from the second interleave processing means by way of a transmission line, as a transmission unit of a unit of data in the third direction.
Also, the above-mentioned packet transmission apparatus preferably further comprises generating means, provided at a preceding stage of the first interleave processing means, for generating a transmission header having a new identifier by deleting predetermined redundancy information from the block information belonging to the plurality of blocks based on the data string, and outputting data including a transmission unit having the generated transmission header to the first interleave processing means.
Further, in the above-mentioned packet transmission apparatus, the transmitting means preferably transmits the transmission unit by an ATM transmission system using the AAL TYPE 1 as an adaptation layer function of an asynchronous transfer mode.
Furthermore, in the above-mentioned packet transmission apparatus, the transmitting means preferably transmits the transmission unit by an ATM transmission system using the AAL TYPE 5 as an adaptation layer function of an asynchronous transfer mode.
According to the third aspect of the present invention, there is provided a packet transmission apparatus comprising first parity adding means for adding a parity for error detection to a predetermined data string in a direction in which the data string is aligned, and outputting, in a predetermined unit of data, the data string to which the parity for error detection is added, first interleave processing means for executing a first interleave process by writing the data string outputted from the first parity adding means into a first storage apparatus having a first matrix form in a first direction of the first matrix, and thereafter, reading from the first storage apparatus the data in a second direction perpendicular to the first direction of the first matrix, and for outputting the data obtained after the first interleave process, in a unit of data in the second direction, second parity adding means for adding a predetermined parity for error correction to data outputted from the first interleave processing means in a unit of data in the second direction, and outputting the data to which the parity for error correction is added, second interleave processing means for executing a second interleave process by writing data outputted from the second parity adding means into a second storage apparatus having a second matrix form in a fourth direction of the second matrix coinciding with the second direction of the first matrix, and thereafter, reading from the second storage apparatus the data in a third direction perpendicular to the fourth direction of the second matrix, and for outputting the data obtained after the second interleave process, in a unit of data in the third direction, and transmitting means for transmitting data outputted from the second interleave processing means by way of a transmission line, as a transmission unit of a unit of data in the third direction.
Also, the above-mentioned packet transmission apparatus preferably further comprises, generating means, provided at a preceding stage of the first parity adding means, for generating a transmission header having a new identifier by deleting predetermined redundancy information from the block information belonging to the plurality of blocks based on the data string, and outputting data including a transmission unit having the generated transmission header to the first parity adding means.
According to the fourth aspect of the present invention, there is provided a packet transmission apparatus for transmitting in a packet form a transmission unit including a data string arranged so as to divide predetermined data into a plurality of blocks, wherein each block has a fixed length. The packet transmission apparatus according to the fourth aspect of the present invention comprises generating means for generating a plurality of transmission headers having a new identifier from block information belonging to a plurality of blocks based on the data string, and outputting data including a transmission unit having the plurality of generated transmission headers, first interleave processing means for executing a first interleave process by writing data outputted from the generating means into a first storage apparatus having a first matrix form in a first direction of the first matrix, and thereafter, reading from the first storage apparatus the data in a second direction perpendicular to the first direction of the first matrix, and for outputting the data obtained after the first interleave process in a unit of data in the second direction, parity adding means for adding a predetermined parity for error correction to data outputted from the first interleave processing means in a unit of data in the second direction, and outputting the data to which said parity for error correction is added, second interleave processing means for executing a second interleave process by writing data outputted from the parity adding means into a second storage apparatus having a second matrix form in a fourth direction of the second matrix coinciding with the second direction of the first matrix, and thereafter, reading from the second storage apparatus the data in a third direction perpendicular to the fourth direction of the second matrix, and for outputting the data obtained after the second interleave process in a unit of data in the third direction, and transmitting means for transmitting data outputted from the second interleave processing means by way of a transmission line, as a transmission unit of a unit of data in the third direction, wherein the generating means arranges the plurality of transmission headers in the data including the transmission unit so that the plurality of transmission headers are positioned in different units of data in the third direction, respectively.
According to the fifth aspect of the present invention, there is provided a packet transmission apparatus for transmitting in a packet form a transmission unit including a data string arranged so as to divide predetermined data into a plurality of blocks, wherein each block has a fixed length. The packet transmission apparatus according to the fifth aspect of the present invention comprises parity adding means for adding a predetermined parity for error correction to the data string in a predetermined unit of data, and outputting the data to which the parity for error correction is added, interleave processing means for executing an interleave process by writing data outputted from the parity adding means into a storage apparatus having a matrix form in a first direction of the matrix, and thereafter, reading from the storage apparatus the data in a second direction perpendicular to the first direction of the matrix, and for outputting the data obtained after the interleave process in a unit of data in the second direction, and transmitting means for transmitting data outputted from the interleave processing means by way of a transmission line, as a transmission unit of a unit of data in the second direction.
Also, in the above-mentioned packet transmission apparatus, the data unit in the second direction is preferably a cell block unit of an asynchronous transfer mode.
Further, the above-mentioned packet transmission apparatus preferably further comprises generating means, provided at a preceding stage of the parity adding means, for generating a transmission header having a new identifier by deleting predetermined redundancy information from the block information belonging to the plurality of blocks based on the data string, and outputting data including a transmission unit having the generated transmission header to the parity adding means.
According to the sixth aspect of the present invention, there is provided a packet transmission apparatus for transmitting in a packet form a transmission unit including a data string arranged so as to divide predetermined data into a plurality of blocks, wherein each block has a fixed length, and wherein block information for specifying a block type is added to each block. The packet transmission apparatus in accordance with the sixth aspect of the present invention comprises generating means for generating a transmission header having a new identifier by deleting predetermined redundancy information from the block information belonging to the plurality of blocks based on the data string, and generating a transmission unit having the generated transmission header, packet forming means for dividing a data string including the transmission unit generated by the generating means, into a plurality of packets in a unit of MPG transport stream packets, and outputting the plurality of packets, and transmitting means for transmitting the plurality of packets outputted from the packet forming means by way of a transmission line.